Substrate-controlled allotropic phases and growth orientation of TiO2 epitaxial thin films

TiO2 thin films were grown by pulsed laser deposition on a wide variety of oxide single‐crystal substrates and characterized in detail by four‐circle X‐ray diffraction. Films grown at 873 K on (100)‐oriented SrTiO3 and LaAlO3 were (001)‐oriented anatase, while on (100) MgO they were (100)‐oriented. On (110) SrTiO3 and MgO, (102) anatase was observed. On M‐plane and R‐plane sapphire, (001)‐ and (101)‐oriented rutile films were obtained, respectively. On C‐plane sapphire, the coexistence of (001) anatase, (112) anatase and (100) rutile was found; increasing the deposition temperature tended to increase the rutile proportion. Similarly, films grown at 973 K on (100) and (110) MgO showed the emergence, besides anatase, of (110) rutile. All these films were epitaxically grown, as shown by ϕ scans and/or pole figures, and the various observed orientations were explained on the basis of misfit considerations and interface arrangement.